Variable Displacement Compressor

ABSTRACT

A variable displacement compressor having a swash plate capable of being changed with inclination angle for converting the rotation of a drive shaft into the reciprocating motion of pistons comprises a plurality of urging means each having one end brought into contact with the swash plate and urging the swash plate in the direction of increasing an inclination angle of the swash plate, wherein the plurality of urging means are constructed so that the number of urgings is increased as the inclination angle of the swash plate is decreased. The freedom of adjustment of the urging force due to the urging means for increasing the inclination angle of the swash plate can be enlarged by a simple structure, and the urging force can be finely adjusted in accordance with the inclination angle of the swash plate. Consequently, the adjustment of the urging force due to the urging means for urging the swash plate in the inclination angle increasing direction can be optimized, and the swash plate can be allowed to perform a desirable operation near the minimum inclination angle.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a swash plate type variable displacement compressor, and specifically, to a variable displacement compressor in which the structure of an urging means portion for urging a swash plate in an inclination angle increasing direction is improved and which is suitable for use in an air conditioning system for vehicles.

BACKGROUND ART OF THE INVENTION

In a swash plate type variable displacement compressor, in order to return the inclination angle of a swash plate from a condition of the minimum inclination angle toward an inclination angle increasing direction and easily make the displacement for discharge of the compressor increase, a structure is known wherein an urging means (an inclination angle increasing spring or a return spring) for urging the swash plate in the inclination angle increasing direction near the position of the minimum inclination angle is provided (for example, Patent document 1).

Prior Art Documents Patent Documents

Patent document 1: JP-A-2000-2180

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As described above, although the inclination angle increasing spring aims essentially to return the displacement from the minimum inclination angle, for example, by appearance of a clutchless compressor, because the urging force of the inclination angle increasing spring influences power consumption at a state where the operation of the compressor is stopped (at a state near the minimum inclination angle), the adjustment of the urging force becomes important.

However, in the inclination angle increasing spring (in particular, an inclination angle increasing spring such as a return spring 27 described in Patent document 1), its urging force changes proportionally (straightly) in accordance with an amount of its deflection, the urging force of the inclination angle increasing spring relative to the swash plate changes in accordance with the inclination angle of the swash plate, but only by this structure wherein the urging force changes proportionally, it is difficult to adjust the urging force finely in accordance with the inclination of the swash plate.

Accordingly, paying attention to the above-described problems in the conventional technology, an object of the present invention is to provide a variable displacement compressor which can enlarge freedom of adjustment of urging force due to urging means for increasing an inclination angle of a swash plate by a simple structure and which can adjust the urging force finely in accordance with the inclination angle of the swash plate.

Means for Solving the Problems

To achieve the above-described object, a variable displacement compressor according to the present invention has a housing in which a discharge chamber, a suction chamber, a crank chamber and cylinder bores are defined therein, pistons disposed in the cylinder bores, a drive shaft supported rotatably in the housing, and a converting mechanism including a swash plate capable of being changed with inclination angle for converting a rotation of the drive shaft into a reciprocating motion of the pistons, which adjusts strokes of the pistons by varying a pressure difference between the crank chamber and the suction chamber, compresses a fluid sucked from the suction chamber into the cylinder bores and discharges a compressed fluid into the discharge chamber, and is characterized in that a plurality of urging means each having one end brought into contact with the swash plate and urging the swash plate in a direction of increasing an inclination angle of the swash plate are provided, and the plurality of urging means are constructed so that a number of urgings is increased as the inclination angle of the swash plate is decreased.

In such a variable displacement compressor, the number of urgings of the urging means is increased as the inclination angle of the swash plate is decreased, thereby increasing the urging force relative to the swash plate, and the freedom of adjustment of the urging force in accordance with the inclination angle of the swash plate is enlarged. By this, the adjustment of the urging force due to the urging means for urging the swash plate in the inclination angle increasing direction can be optimized. Although the plurality of urging means urge the swash plate in parallel with each other, because each urging means may be formed as a simple structure, even the whole of the plurality of urging means can be formed as a simple structure. Further, since the plurality of urging means urge the swash plate in parallel with each other, the length of the urging means in the axial direction of the compressor may be small, and by providing the plurality of urging means, the axial length of the compressor itself is not increased.

In the above-described variable displacement compressor according to the present invention, for example, a structure may be employed wherein each of the plurality of urging means is constructed so that an urging force is proportionally increased as the inclination angle of the swash plate is decreased, and by increasing the number of urgings as described above, a gradient of increase of urging force due to the plurality of urging means is increased. In such a structure, because the urging force increases proportionally, the adjustment of the urging force is facilitated. At the same time, because the gradient of increase of urging force can be set great, a fine adjustment of the urging force becomes possible.

Further, a structure may be employed wherein a connecting means is provided for connecting the plurality of urging means integrally. In such a structure, because the plurality of urging means are connected integrally by the connecting means, these urging means can be treated as an integrated single member, and therefore, the assembly is facilitated and the productivity is improved.

Further, a structure may be employed wherein a positioning structure for positioning the above-described connecting means in an axial direction of the drive shaft is formed on the connecting means and the drive shaft, and at least two of the plurality of urging means are set so as to be different from each other with height in an axial direction from the connecting means. In such a structure, the position, in the axial direction, of the connecting means is decided by the above-described positioning structure, and because the heights in the axial direction of at least two of the plurality of urging means are set to be different from each other referring to the positioned connecting means as a base position, the number of urgings of the urging means can be changed in accordance with the inclination angle of the swash plate more precisely and more securely.

Further, a structure may also be employed wherein the above-described plurality of urging means are formed, for example, as flat springs, the flat springs are made from a flat spring forming material by pressing, and the connecting means is formed on a remaining part of the flat spring forming material other than the flat springs. In such a structure, since the flat springs and the connecting means can be formed as a single member, it becomes possible to substantially simultaneously form the flat springs and the connecting means by pressing, and the manufacture may be facilitated and it may contribute reduction in cost.

Further, a structure may also be employed wherein the above-described connecting means and the plurality of urging means are formed so as to surround the drive shaft, the plurality of urging means are arranged at predetermined intervals, and respective tip portions thereof urge the swash plate in the inclination increasing direction and respective base portions thereof are connected integrally with the connecting means. In such a structure, since the connecting means is formed so as to surround the drive shaft and the plurality of urging means can be disposed around the drive shaft at predetermined intervals, even if there are a plurality of urging means, they can be disposed compactly. Therefore, it becomes possible to make the whole of the urging means portion small-sized and simplify the structure.

Further, a structure may also be employed wherein at least two of the above-described plurality of urging means are set so that spring constants thereof are different from each other. In particular, if this structure is applied to a case where the plurality of urging means are formed as flat springs, the freedom of adjustment of spring properties of the flat springs can be enlarged, and optimization of adjustment of urging force may be facilitated.

Further, a structure may also be employed wherein a minimum inclination angle regulating means for regulating a mechanical minimum inclination angle of the swash plate is provided, and the minimum inclination angle regulating means is connected integrally to the above-described connecting means. In such a structure, it becomes possible to manage the urging force of the urging means by taking the minimum inclination angle as a standard and to reduce dispersion of the urging forces between the urging means. Further, since the minimum inclination angle regulating means can function also as a regulating means for regulating an excessive deflection of the urging means, it becomes possible that an excessive stress does not operate to the urging means, and it can contribute to ensure the reliability of the urging means.

The variable displacement compressor according to the present invention is suitable particularly for a case where the fluid to be compressed is refrigerant, and in particular, suitable as a compressor used in an air conditioning system for a vehicle.

EFFECT ACCORDING TO THE INVENTION

In the variable displacement compressor according to the present invention, since a plurality of urging means for urging the swash plate in the inclination angle increasing direction and the number of urgings is increased as the inclination angle of the swash plate is decreased, the freedom of adjustment of urging force of the urging means for increasing the inclination angle of the swash plate can be enlarged while a simple and compact structure is employed, and a fine adjustment of urging force can be carried out in accordance with the inclination angle of the swash plate. Consequently, the adjustment of the urging force due to the urging means for urging the swash plate in the inclination angle increasing direction can be optimized, and the swash plate can be allowed to perform a desirable operation near the minimum inclination angle.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 shows a vertical sectional view of a variable displacement compressor according to an embodiment of the present invention (FIG. 1 (A)) and a sectional view of a displacement control valve for controlling a displacement thereof (FIG. 1 (B)).

FIG. 2 is a vertical sectional view of the displacement control valve depicted in FIG. 1.

FIG. 3 shows flat springs in the variable displacement compressor depicted in FIG. 1, FIG. 3 (A) is an elevational view of the flat springs, and FIG. 3 (B) is a side view of FIG. 3 (A).

FIG. 4 is an enlarged partial sectional view of the variable displacement compressor depicted in FIG. 1, showing a state where a swash plate comes into contact with a stopper.

FIG. 5 is a diagram showing a relationship between a displacement of spring and a spring force of the flat spring depicted in FIG. 3.

FIG. 6 is a diagram showing a relationship between a resultant force of a coil spring and a flat spring and an inclination angle of a swash plate in a case where the flat spring depicted in FIG. 3 is used.

FIG. 7 is a diagram showing a relationship between a resultant force of a coil spring and flat springs and an inclination angle of a swash plate in a case where the flat spring portion uses two flat springs.

FIG. 8 is a diagram showing a relationship between a resultant force of a coil spring and flat springs and an inclination angle of a swash plate in a case where the flat spring portion uses four flat springs.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, desirable embodiments of the present invention will be explained referring to figures.

FIG. 1 shows a variable displacement compressor according to an embodiment of the present invention (FIG. 1 (A)) and a displacement control valve for controlling a displacement of the compressor (FIG. 1 (B)). In FIG. 1, a swash plate type variable displacement compressor 100 as the variable displacement compressor comprises a cylinder block 101 having a plurality of cylinder bores 101 a, a front housing 102 provided on one end of cylinder block 101, and a rear housing 104 provided on the other end of cylinder block 101 via a valve plate 103.

A drive shaft 106 is disposed crossing the inside of a crank chamber 105 defined by cylinder block 101 and front housing 102. A swash plate 107 is connected to a rotor 108 fixed to drive shaft 106 via a connecting part 109, and it is supported rotatably together with drive shaft 106 and at a condition capable of being changed with its inclination angle relative to drive shaft 106. A coil spring 110 urging swash plate 107 toward a direction for decreasing the inclination angle is disposed between rotor 108 and swash plate 107. At a side of swash plate 107 opposite to the side of coil spring 110, a flat spring 111 is disposed for urging swash plate 107, which is in a condition of the minimum inclination angle, in a direction of increasing the inclination angle. As described later, this flat spring 111 is constructed as a member having flat spring portions 111 a 1, 111 a 2, 111 a 3 provided as a plurality of urging means for urging swash plate 107 in the inclination angle increasing direction in the present invention.

One end of drive shaft 106 extends to the outside of the housing through a boss portion 102 a of front housing 102, and it is connected to a drive source such as a vehicle engine (not shown) through a belt and the like via a power transmission (not shown). A shaft sealing device 112 is disposed between drive shaft 106 and boss portion 102 a. Drive shaft 106 is supported by bearings 113, 114, 115, 116 in the radial direction and in the thrust direction.

Pistons 117 are disposed in cylinder bores 101 a, and a pair of shoes 118 contained in a recessed portion 117 a in one end portion of each piston 117 support the outer circumferential part of swash plate 107 at a relative sliding condition. The rotation of drive shaft 106 is converted into reciprocal motion of pistons 117 via swash plate 107 and shoes 118.

A suction chamber 119 and a discharge chamber 120 are formed in rear housing 104. Suction chamber 119 communicates with cylinder bore 101 a via a suction hole 103 a formed in valve plate 103 and a suction valve (not shown), and discharge chamber 120 communicates with cylinder bore 101 a via a discharge valve (not shown) and a discharge hole 103 b formed in valve plate 103. Suction chamber 119 is connected to an evaporator of an air conditioning system for a vehicle (not shown) via a suction port 104 a.

Front housing 102, cylinder block 101, valve plate 103 and rear housing 104 cooperate to form a housing containing a compression mechanism formed by drive shaft 106, rotor 108, connection part 109, swash plate 107, shoes 118, pistons 117, cylinder bores 101 a, suction valves, discharge valves, etc.

A muffler 121 is disposed outside cylinder block 101. Muffler 121 is formed by connecting a cup-like cylindrical lid member 122, provided as a separate member from cylinder block 101, to a cylindrical wall 101 b stood on the outer surface of cylinder block 101 via a seal member. A discharge port 122 a is formed in lid member 122. Discharge port 122 a is connected to a condenser of an air conditioning system for a vehicle (not shown).

A communication path 123 communicating muffler 121 with discharge chamber 120 is formed over cylinder block 101, valve plate 103 and rear housing 104. Muffler 121 and communication path 123 form a discharge path extending between discharge chamber 120 and discharge port 122 a, and the muffler 121 forms an enlarged space disposed on the way of the discharge path. Then, a check valve 200 for opening/closing the inlet of muffler 121 is disposed in muffler 121.

The above-described front housing 102, cylinder block 101, valve plate 103 and rear housing 104 are adjacent to each other via gaskets (not shown), and assembled integrally using a plurality of through bolts.

A displacement control valve 300 is attached to rear housing 104. Displacement control valve 300 adjusts an opening degree of communication path 124 between discharge chamber 120 and crank chamber 105, and controls an amount of discharged refrigerant gas introduced into crank chamber 105. The refrigerant gas in crank chamber 105 flows into suction chamber 119 through a gap between bearings 115, 116 and drive shaft 106, a space 125 formed in cylinder block 101 and an orifice 103 c formed in valve plate 103.

The internal pressure of crank chamber 105 is changed by displacement control valve 300, thereby variably controlling the displacement for discharge of swash type variable displacement compressor 100. Displacement control valve 300 adjusts the amount of electricity sent to the incorporated solenoid based on an external signal, variably controls the displacement for discharge of swash type variable displacement compressor 100 so that the internal pressure of suction chamber 119 introduced into a pressure sensing chamber of displacement control valve 300 through communication path 126 becomes a predetermined value, further, forcibly opens communication path 124 by turning the electric current to the incorporated solenoid OFF, and by that, controls the displacement for discharge of swash type variable displacement compressor 100 to become minimum. Displacement control valve 300 can control the suction pressure at an optimum value in accordance with an external environment.

As shown in FIG. 2, displacement control valve 300 comprises a first pressure sensing chamber 302 which is formed in a valve housing 301 and which communicates with crank chamber 105 through communication hole 301 a, a valve hole 301 c one end of which opens to first pressure sensing chamber 302 and the other end of which opens to a valve chamber 303 communicating with discharge chamber 120 through communication hole 301 b, a cylindrical valve body 304 one end portion of which is disposed in valve chamber 303 and opens/closes valve hole 301 c and the other end portion of which is supported slidably at supporting hole 301 d, a bellows assembly 305 which is disposed in first pressure sensing chamber 302, which receive a crank chamber pressure through communication hole 301 a and which functions a pressure sensing means the inside of that is vacuumed and in that a spring is disposed, a connection part 306 to one end of which bellows assembly 305 is connected at a condition capable of being brought into contact therewith/apart therefrom and the other end of which is fixed to one end of valve body 304, and a second pressure sensing chamber 307 in which the other end of valve body 304 is disposed and which communicates with suction chamber 119 through communication hole 301 e.

Supporting hole 301 d slidably supporting the other end portion of valve body 304 is formed in valve housing 301, and by a condition where valve body 304 is supported slidably by supporting hole 301 d via a fine gap, the other end of valve body 304 is interrupted from valve chamber 303.

Displacement control valve 300 further comprises a solenoid rod 304 a which is formed integrally with valve body 304 and to which a movable iron core 308 is fitted and fixed at the end distanced from valve body 304, a fixed iron core 309 into which solenoid rod 304 a is inserted and which is disposed confronting movable iron core 308 with a predetermined gap, a spring 310 which is disposed between fixed iron core 309 and movable iron core 308 and which urges movable iron core 308 in a valve opening direction, a cylindrical member 312 made from a non-magnetic material which is fixed to solenoid case 311 at a condition being inserted with fixed iron core 309 and movable iron core 308, and an electromagnetic coil 313 which surrounds cylindrical member 312 and which is contained in solenoid case 311.

With the operation of this displacement control valve 300, since a bellows effective area Sb of bellows assembly 305, a pressure receiving area Sv of the pressure of crank chamber 105 which operates to valve body 304 and which is received from the side of valve hole 301 c, and a pressure receiving area Sr of the suction pressure which operates to valve body 304 at second pressure sensing chamber 307, are set at approximately same values, the force operating to valve body 304 is determined by the following equation (1).

Ps=[−(1/Sb)·F(i)+(F+f)/Sb]  (1)

Where,

Ps: pressure of suction chamber Sb: bellows effective area (=pressure receiving area (Sv) of the pressure of crank chamber operating to valve body=pressure receiving area (Sr) of the pressure of suction chamber operating to valve body) f: urging force of spring 310 F: urging force of bellows F(i): electromagnetic force

Further, in displacement control valve 300, if the pressure of suction chamber Ps is lower than the value determined by the above-described equation (1), bellows 305 a expands, valve body 304 leaves away from the valve seat to open valve hole 301 c, first pressure sensing chamber 302 and valve chamber 303 are communicated with each other through valve hole 301 c, and communication path 124 between discharge chamber 120 and crank chamber 105 is opened. The refrigerant in discharge chamber 120 is supplied to crank chamber 105 through communication path 124, the pressure of crank chamber increases, the inclination angle of swash plate 107 decreases and the displacement for discharge of variable displacement compressor 100 decreases, and the pressure of suction chamber elevates. If the pressure of suction chamber is higher than the value determined by the above-described equation (1), the bellows of bellows assembly 305 contracts, valve body 304 comes into contact with the valve seat to close valve hole 301 c, the communication between first pressure sensing chamber 302 and valve chamber 303 through valve hole 301 c is interrupted, and communication path 124 between discharge chamber 120 and crank chamber 105 is closed. The refrigerant gas in crank chamber 105 flows out into suction chamber 119 through gaps between bearings 115, 116 and drive shaft 106, space a25 formed in cylinder block 101 and orifice hole 103 c formed in valve plate 103 and the pressure of crank chamber is reduced, the inclination angle of swash plate 107 increases and the displacement for discharge of compressor 100 increases, and the pressure of suction chamber decreases. The pressure sensing mechanism formed by bellows assembly 305, connecting part 306 and valve body 304 automatically controls the pressure of suction chamber at the value determined by the equation (1). The electromagnetic actuator formed by solenoid rod 304 a, movable iron core 308, fixed iron core 309, spring 310, solenoid case 311, cylindrical member 312 and electromagnetic coil 313 changes the operation point of the pressure sensing mechanism in accordance with the value “I” of electric current flowing in electromagnetic coil 313.

In displacement control valve 300, when the electric current “I” supplied to electromagnetic coil 313 increases, can be obtained a control property in that the pressure of suction decreases. In displacement control valve 300, the aforementioned pressure sensing mechanism and the electromagnetic actuator drive valve body 304. By the structure where displacement control valve 300 has the pressure sensing mechanism, the control accuracy of the suction chamber pressure is improved, and by the structure where the electromagnetic actuator for changing the operation point of the pressure sensing mechanism is provided, it becomes possible to decide the suction chamber pressure to be controlled, univocally relative to the control electric current “i”.

Further, if the supply of electricity to the solenoid is turned to be OFF, valve body 304 opens valve hole 301 c by the urging force of spring 310, the refrigerant in discharge chamber 120 is supplied to crank chamber 105 through communication path 124, the pressure of crank chamber increases and the inclination angle of swash plate 107 decreases, and the displacement for discharge of variable displacement compressor 100 becomes minimum.

Next, referring to FIGS. 3 to 6, flat spring 111 will be explained.

In this embodiment, as shown in FIGS. 3 and 4, flat spring 111 is constructed so that flat spring portions 111 a 1, 111 a 2, 111 a 3 provided at three positions in the circumferential direction, stoppers 111 b provided at three positions, and a connecting portion 111 c annularly formed for connecting three flat spring portions 111 a 1, 111 a 2, 111 a 3 and three stoppers 111 b, are connected integrally. Namely, this flat spring 111 is constructed as a member which connects flat spring portions 111 a 1, 111 a 2, 111 a 3 at three positions provided as a plurality of urging means for urging swash plate 107 in an inclination angle increasing direction in the present invention and stoppers 111 b at three positions provided as a minimum inclination angle regulating means for regulating the mechanical minimum inclination angle of swash plate 107 in the present invention, integrally with each other, by a connecting portion 111 c provided as a connecting means in the present invention. This flat spring is formed from a flat spring forming material (a flat spring forming plate) by pressing, and stoppers 111 b and connecting portion 111 c are formed at the remaining part other than the respective flat spring portions 111 a 1, 111 a 2, 111 a 3. Where, three flat spring portions 111 a 1, 111 a 2, 111 a 3 are disposed at approximately same intervals around drive shaft 106.

In flat spring 111, as shown in FIG. 4, inner diameter portion 111 d (shown in FIG. 3 (A)) of connecting portion 111 c is fitted onto drive shaft 106, flat spring 111 is positioned in the axial direction by being brought into contact with a stepped portion formed on drive shaft 105, and it is fixed by a snap ring 150. By, a condition where swash plate 107 comes into contact with the tips of stoppers 111 b, the mechanically regulated minimum inclination angle (θ min) of swash plate 107 is defined. For example, as shown in FIG. 6, when the angle of swash plate 107 is referred to be 0 degree at a state where the plane of swash plate 107 is perpendicular to the axis of drive shaft 106, the minimum inclination angle (θ min) is set at approximately 0 degree (an angle near 0 degree), and the height os three stoppers 111 b are set targeting this minimum inclination angle (θ min).

Further, although an urging force for urging swash plate 107 in the inclination angle increasing direction operates by a condition where the tips of the respective flat spring portions 111 a 1, 111 a 2, 111 a 3 come into contact with swash plate 107, the inclination angles of swash plate 107, at the tips of the respective flat spring portions 111 a 1, 111 a 2, 111 a 3 come into contact with swash plate 107, are set so as to be different from each other depending upon the respective flat spring portions. As shown in FIG. 3 (B), this can be securely achieved by setting the heights in the axial direction of the tips of the respective flat spring portions 111 al, 111 a 2, 111 a 3 from connecting portion 111 c at heights different from each other (h1>h2>h3).

Further, because the tips of stoppers 11 b are also managed with the heights from connecting portion 111 c, dispersion of urging forces of flat spring 111 from the minimum inclination angle is decreased. Where, since stoppers 111 c also function regulating means for regulating excessive deflections of flat spring portions 111 a 1, 111 a 2, 111 a 3, an excessive stress is not applied to flat spring portions 111 a 1, 111 a 2, 111 a 3.

The urging force of flat spring 111 becomes, for example, as shown in FIG. 5. For example, when flat spring 111 is pushed by a pushing body having a pushing surface with an outer diameter of flat spring 111 or more (the displacement when the pushing body comes into contact with flat spring portion 111 a 1 is referred to as zero), although, up to a condition where the displacement of flat spring portion 111 a 1 becomes ×1, only flat spring portion 111 a 1 functions as a spring and the urging force increases proportionally, when it exceeds ×1, flat spring portion 111 a 2 also comes into contact and the urging force of flat spring portion 111 a 2 is added, and therefore, the inclination (gradient) of increase of the urging force becomes greater. Further, when the displacement exceeds ×2, flat spring portion 111 a 3 also comes into contact and the urging force of flat spring portion 111 a 3 is added, and therefore, the gradient of increase of the urging force becomes further greater. Namely, by the number of urgings due to the flat spring portions being increased, a property in that the spring constant becomes greater at a stepped-up condition is given. Therefore, by setting ×1, ×2 at adequate positions, the load property can be adjusted, and the urging force may be optimized.

When the inclination angle of swash plate 107 becomes smaller than the predetermined angle θ₁, swash plate 107 was nipped by coil spring 110 and flat spring 111, and the resultant force of both springs becomes as shown in FIG. 6. In FIG. 6, only flat spring 111 a 1 functions as a spring in a zone between θ₁ and θ₂, flat springs 111 a 1 and 111 a 2 function as springs in a zone between θ₂ and θ₃, and all of flat springs 111 a 1, 111 a 2 and 111 a 3 function as springs in a zone between θ₃ and θ min. Where, θ₄ is an angle at which the resultant force of both springs becomes zero, in a zone below θ₄, an urging force for urging swash plate 107 in the inclination angle increasing direction operates, and in a zone more than θ₄, an urging force for urging swash plate 107 in the inclination angle decreasing direction operates

Thus, the tip sides of flat spring portions Mal, 111 a 2, 111 a 3 whose heights from connecting portion 111 c are different from each other come into contact with swash plate 107 in order, and by employing a structure wherein the number of urgings increases in order, a finely adjusted desirable property can be given to flat spring 111 as the urging force for urging swash plate 107 in the inclination angle increasing direction.

In the above-described embodiment, although the heights of the respective flat spring portions are set to be different from each other, a structure may be employed wherein the heights of the respective flat spring portions are set to be same, a step is provided to a side of the swash plate with which the respective flat spring portions are brought into contact, and the number of urgings of the respective flat spring portions is increased in order as the inclination angle of the swash plate is decreased. In such a structure, forming of the flat spring portions is facilitated.

Further, in the above-described embodiment, although a case, where the number of a plurality of urging means is three, is shown, any number of urging means is available as long as it is two or more. For example, with respect to a property of spring resultant force, FIG. 7 shows an example of two urging means and FIG. 8 shows an example of four urging means, respectively, and thus, the number of urgings may be decided in consideration of optimization of adjustment of urging force.

Further, in the above-described embodiment, although the lengths of arms of the plurality of flat spring portions 111 a 1, 111 a 2, 111 a 3 are set to be same and the heights thereof are changed, a structure may be employed wherein the lengths of arms of the respective flat spring portions are set to be different from each other and the respective spring constants are set to be different from each other. By such a setting, the freedom of adjustment of the spring property of flat spring 111 can be further enlarged, and optimization of the adjustment of urging force may be facilitated.

Further, the plurality of urging means are not limited to flat springs. For example, a structure may be employed wherein compression coil springs are disposed around the drive shaft, one ends thereof are brought into contact with the swash plate, and the other ends are connected by a connecting portion. Alternatively, a structure may be employed wherein a drive shaft is inserted into a plurality of compression coil springs disposed concentrically, one ends of the coil springs are brought into contact with the swash plate, and the other ends are connected by a connecting portion.

Further, in the above-described embodiment, although the plurality of flat spring portions 111 a 1, 111 a 2, 111 a 3 are formed toward the circumferential direction of the drive shaft as shown in FIG. 3 (A), forming of flat spring portions is not limited thereto. For example, a structure may be employed wherein the tip portions of the respective flat spring portions are formed so as to be directed toward an axis of the drive shaft, or formed toward a direction apart from the drive shaft.

Further, a structure can also be employed wherein a rotation preventing mechanism is provided so that flat spring 111 is not rotated relative to drive shaft 106, for example, wherein a groove is defined on the drive shaft and a part of flat spring 111 is engaged with the groove.

Further, in a case of a structure where a swash plate supporting member such as a sleeve, a hinge ball, etc. is provided between swash plate 107 and drive shaft 106, the swash plate supporting member may be urged by flat spring portions 111 a 1, 111 a 2, 111 a 3.

Further, the present invention may also be applied to a variable displacement compressor attached with an electromagnetic clutch or a clutchless compressor, and the present invention may also be applied to a variable displacement compressor driven by a motor, for example, a motor built-in variable displacement compressor.

Furthermore, in the above-described embodiment, although a case where the fluid to be compressed is refrigerant has been explained, another fluid to be compressed may be used. Further, the kind of the refrigerant as the fluid to be compressed is not particularly limited, the present invention can be applied commonly to variable displacement compressors for which carbon dioxide or another new refrigerant can be used, other than a case where R134 a is used as refrigerant.

INDUSTRIAL APPLICATIONS OF THE INVENTION

The variable displacement compressor according to the present invention can be applied to any compressor having a swash plate capable of being changed with inclination angle, and in particular, it is suitable as a variable displacement compressor used in an air conditioning system for a vehicle.

EXPLANATION OF SYMBOLS

-   100: variable displacement compressor -   101: cylinder block -   101 a: cylinder bore -   102: front housing -   103: valve plate -   104: rear housing -   105: crank chamber -   106: drive shaft -   107: swash plate -   108: rotor -   109: connecting part -   110: coil spring -   111: flat spring having a plurality of urging means -   111 a 2, 111 a 3: flat spring portion as urging means for urging a     swash plate in an inclination angle increasing direction -   111 b: stopper as a minimum inclination angle regulating means for     regulating a mechanical minimum inclination angle of a swash plate -   111 c: connecting portion as a connecting means between a minimum     inclination angle regulating means and urging means -   111 d: inner diameter portion of connecting portion -   117: piston -   118: shoe -   119: suction chamber -   120: discharge chamber -   121: muffler -   122: lid member -   123: communication path -   150: snap ring -   200: check valve -   300: displacement control valve -   301: valve housing -   302: first pressure sensing chamber -   303: valve chamber -   304: valve body -   304 a: solenoid rod -   305: bellows assembly -   307: second pressure sensing chamber -   308: movable iron core -   309: fixed iron core -   311: solenoid case -   313: electromagnetic coil 

1. A variable displacement compressor having a housing in which a discharge chamber, a suction chamber, a crank chamber and cylinder bores are defined therein, pistons disposed in said cylinder bores, a drive shaft supported rotatably in said housing, and a converting mechanism including a swash plate capable of being changed with inclination angle for converting a rotation of said drive shaft into a reciprocating motion of said pistons, which adjusts strokes of said pistons by varying a pressure difference between said crank chamber and said suction chamber, compresses a fluid sucked from said suction chamber into said cylinder bores and discharges a compressed fluid into said discharge chamber, characterized in that a plurality of urging means each having one end brought into contact with said swash plate and urging said swash plate in a direction of increasing an inclination angle of said swash plate are provided, and said plurality of urging means are constructed so that a number of urgings is increased as said inclination angle of said swash plate is decreased.
 2. The variable displacement compressor according to claim 1, wherein each of said plurality of urging means is constructed so that an urging force is proportionally increased as said inclination angle of said swash plate is decreased, and by increasing said number of urgings, a gradient of increase of urging force due to said plurality of urging means is increased.
 3. The variable displacement compressor according to claim 1, wherein a connecting means is provided for connecting said plurality of urging means integrally.
 4. The variable displacement compressor according to claim 3, wherein a positioning structure for positioning said connecting means in an axial direction of said drive shaft is formed on said connecting means and said drive shaft, and at least two of said plurality of urging means are set so as to be different from each other with height in an axial direction from said connecting means.
 5. The variable displacement compressor according to claim 3, wherein said plurality of urging means are formed as flat springs, said flat springs are made from a flat spring forming material by pressing, and said connecting means is formed on a remaining part of said flat spring forming material other than said flat springs.
 6. The variable displacement compressor according to claim 5, wherein at least two of said plurality of urging means are set so that spring constants thereof are different from each other.
 7. The variable displacement compressor according to claim 3, wherein said connecting means and said plurality of urging means are formed so as to surround said drive shaft, said plurality of urging means are arranged at predetermined intervals, and respective tip portions thereof urge said swash plate in said inclination increasing direction and respective base portions thereof are connected integrally with said connecting means.
 8. The variable displacement compressor according to claim 7, wherein at least two of said plurality of urging means are set so that spring constants thereof are different from each other.
 9. The variable displacement compressor according to claim 3, wherein a minimum inclination angle regulating means for regulating a mechanical minimum inclination angle of said swash plate is provided, and said minimum inclination angle regulating means is connected integrally to said connecting means.
 10. The variable displacement compressor according to claim 1, wherein said fluid to be compressed is refrigerant.
 11. The variable displacement compressor according to claim 1, wherein said compressor is used in an air conditioning system for a vehicle. 